Eccentric gear backlash take-up mechanism for seat latches

ABSTRACT

A vehicular seat back recliner hinge comprises first and second hinged members that are mutually rotatably arranged about a common pivot. The first member has a gear rack arranged thereon which is adapted to be engaged by a pinion spur gear. The pinion spur gear is fixed on an adjacent ratchet wheel spur gear in mutually dependent rotatable relation about a common concentric shaft secured on a second hinged member. A selected one of the above-mentioned shaft and pivot are eccentrically mounted on a rotatable bushing arranged on a corresponding one of the members. The bushing is operable to selectively position the pinion spur gear and the rack in first mutually proximal and second mutually spaced positions. A locking pawl arranged on a second of the members is adapted to lockingly engaged with and unlockingly disengage from the ratchet wheel spur gear. In this way, the backlash between the rack and pinion is reduced when the locking pawl, the ratchet wheel spur gear, the pinion spur gear, and the rack are serially engaged in mutually secured relation to resist relative rotation between the two hinged members, about their common pivot. In addition, this arrangement permits backlash to be increased between the pinion spur gear and the rack when the locking pawl is serially disengaged from the ratchet wheel spur gear, in order to ease the relative rotation of the two hinged members about their common pivot.

FIELD OF THE INVENTION

The present invention relates to vehicular seat back hinges, andespecially to a hinge having an adjustable backlash feature for takingup backlash between an automotive seat back hinge rack and pinion.

BACKGROUND OF THE INVENTION

In vehicular seats, and especially in automotive seat manufacturing,hinged recliner mechanisms are generally well known. Typically, suchrecliners provide some form of manual locking and unlocking between aside plate pawl with a seat back rack to facilitate making selectiveincremental adjustments to the inclination of the backrest, relative tothe seat cushion.

Typically, incremental rates of adjustment are either 2 degrees orthree-quarters of a degree.

Due to the inherent practical limitations of typical mass productiontechniques, the three-quarter degree incremental adjustment usuallyemploys a spur gear assembly intermediate between the locking pawl andthe back support arm rack. The spur gear assembly comprises pinion andratchet wheel spur gears that are fixed to one another, and are mutuallyrotatable about a common concentric shaft. The ratio of their respectivediameters and teeth sizes is relied upon to achieve the fine incrementaladjustment rate.

Although such a spur gear assembly is necessary in order to achieve thisfine adjustment rate, their presence contributes significantly to aproblem known in the art as "chuck".

The problem of chuck arises inherently in any mechanical seat backdevice. It is the result of the clearances that are necessarily a partof any device containing parts adapted to undergo relative movement."Clearance" is the difference in size between mating parts prior totheir assembly. Typically the clearance on cylindrical parts may beexpressed as radial clearance or diametrical clearance. Positiveclearance implies that the inside dimension of the female part is largerthan the corresponding outside dimension of the male part. In typicalmechanical applications a running fit requires about 0.001 inches ofpositive radial clearance for a one inch diameter shaft. A clearance of0.003 inches on a one inch shaft is considered to be a loose fit. Inmass production techniques typical of those used in automotive seat backhinge manufacture, positive clearances of 0.008 inches are not at alluncommon.

The amount of clearance typically found in seat back hinges of the typeabove-described, introduce an element of play that is referred to as"chuck". Note that "chuck" is not the "play" which is introduced throughthe flexure of any mechanical components. Rather, the term is expresslyused and understood in the automobile seat back art to mean thecomponent of play which results from mechanical lost motion due toclearance between interconnected parts, when leverage forces are appliedacross the seat back hinge.

"Chuck" is a highly undesirable characteristic in automobile seat backhinges, for both safety and aesthetic reasons. In fact, any increase inchuck, from the marketing point of view, is in diametric opposition withthe very purpose of providing the much larger variation in possibleselectable seat positioning that is achieved with the above-mentionedfiner incremental adjustment rates.

The increase in chuck that is occasioned when the spur gear assembly isincluded in seat back recliner hinges arises partly due to theclearances between the mating teeth of the pawl/ratchet wheel and thepinion/rack, and partly due to the clearances between the spur gearassembly shaft and the holes in the side plate through which the shaftusually extends.

The clearances between the mating gear teeth in known as backlash.Backlash is a necessary characteristic of all mating gear teeth, and isneeded to give the gears enough freedom to mesh and release during therelative motion between any two contacting gear faces.

In the past, attempts have been made to minimize the amount of backlashthat contributes to chuck in seat back hinges, by mounting the spur gearassembly shaft between two spur gear subassembly side plates. During themanufacture of the recliner hinge, this spur gear subassembly is jammedinto forced engagement with the rack on the seat back support arm, in anattempt to minimize the backlash clearance between the respectivecontacting gear faces. The subassembly side plates are then welded intoplace on the adjacent hinge side plates to secure the gear faces with aminimum of backlash clearance.

While this reduces the amount of backlash, and therefore has some effecton reducing chuck, it also reduces the operating clearance between thegear faces during seat back adjustment operations. In fact, thissolution so increases the amount of friction and binding between thegear faces, as to routinely require that a much larger power spring beused in the recliner. Noisy, rough operation is also a by-product ofthis approach to the problem, and this too is inconsistent with themarketing of the higher quality, (i.e. more adjustable) seat backrecliner features associated with upscale automobiles.

Accordingly, there remains a need in the art for improved vehicular seatback recliners.

SUMMARY OF THE INVENTION

Broadly speaking, a vehicular seat back recliner hinge is provided whichincludes a releasably lockable hinge mechanism for selectivelypositioning a pair of mutually opposed, interlockably cooperative gearfaces which are secured on respective ones of first and second hingemembers. These hinge members are mutually relatively rotatable about acommon pivot. The mechanism in question comprises one such gear facesupported on a first hinge member in eccentrically offset relation froma rotational center on a selectively rotatably bushing, together withanother such gear face operably positioned to cooperatively engage inreleasably locked relation with the first above-mentioned, one such gearface, when the bushing is selectively rotated to effect an eccentricallymotivated positional translation of the one such gear face into aninferior conjunction with another such gear face.

In its broadest aspects, the present invention contemplates embodimentsin which the two gear faces are moved into and out of contacting,cooperative engagement, through the selective positional translationeffected by way of the eccentric bushing. Such embodiments would includevehicular seat back hinges which may or may not also include pinion andratchet spur wheel subassemblies. As has already been mentionedhereinbefore, however, there is a very real and substantial need forvehicular seat back hinges in which pinion spur gear backlash isadjustable to facilitate freer rotation of the seat back duringrotational adjustment of the hinge.

In accordance with a particularly preferred and advantageous aspect ofthe present invention, therefore, there is provided a vehicular seatback recliner hinge adapted for the selective incremental adjustment ofthe inclination of a back rest relative to a seat cushion. The presenthinge comprises first and second hinge members which are mutuallyrotatably arranged about a common pivot. The first such member has agear rack arranged thereon which is adapted to be engaged by a pinionspur gear. The pinion spur gear is fixed to an adjacent ratchet wheelspur gear in mutually dependent rotatable relation therewith about acommon concentric shaft that is secured on the second of theabove-mentioned members.

A selected one of the shaft and the pivot are eccentrically mounted on arotatable bushing which is arranged on a corresponding one of themembers. The bushing is operable to selectively position the pinion spurgear and the rack in one of first mutually proximal and second mutuallyspaced positions. Note that in the second mutually spaced positions, thetwo gear faces are not necessarily arranged in a non-contactingrelation. It is sufficient that the contacting relation between the twofaces in the second position result in a reduction in backlash.

A locking pawl is arranged on the second of the members, and is adaptedto lockingly engage with and unlockingly disengage from the ratchetwheel spur gear. The locking pawl is operably positionable in selectedfirst locking and second unlocking positions corresponding to concurrentfirst mutually proximal and second mutually spaced positions of theabove-mentioned rack and pinion. In accordance with the above-describeddevice, it is possible to selectively reduce backlash between the pinionand the rack when the locking pawl, the ratchet wheel spur gear and thepinion spur gear and the rack are serially engaged in mutually securedrelation, so as to prevent the relative rotation between the two membersabout their common pivot. Moreover, it is possible to increase thebacklash clearance between the pinion spur gear and the rack when thelocking pawl is serially disengaged from the ratchet wheel spur gear,and this thereby facilitates relative ease of rotation of the twomembers about their common pivot.

Typically, the first member hereinbefore described will be a seat backsupport arm, while a second member will be a seat cushion assembly sideplate. Moreover, it is preferred that the shaft be eccentrically mountedon the rotatable bushing, and that the bushing be arranged on the sideplate.

Preferably, the locking pawl and the rotatable bushing are co-operablylinked to concurrently, and respectively:

engage the ratchet wheel spur gear, and eccentrically rotate the pinionspur gear into proximal relation with the rack wherein all of theabove-mentioned components are arranged in their respective firstpositions; and,

disengage the ratchet wheel spur gear and eccentrically rotate thepinion gear into spaced relation from the rack, wherein all of theabove-mentioned components are located in their respective secondpositions.

Typically, a cam assembly is pivotally arranged on the side plate with arotational spring bias adapted to normally rotate a cam surface intofirst contacting relation with a cam follower surface on the lockingpawl. This biases the locking pawl into the first locking position. Thecam assembly is manually operable however, to be rotatable contrary tothe rotational spring bias, and into a second contacting relation withanother cam follower surface of the locking pawl, which is adapted tomove the locking pawl into the second unlocking position. The rotatablebushing is also normally spring biased in order to position the pinionspur gear and the rack into the first proximal position. An extension ofthe cam assembly has another cam surface which acts concurrently (i.e.during the manual operation of the cam assembly as a whole), on a camfollower surface of the rotatable bushing. In this way the bushing isrotated to thereby eccentrically position the pinion spur gear and therack in their second relatively spaced position. Preferably, the springbias on the cam and the rotatable bushing are provided by a commonspring acting in tension between lever arms on respective ones of thecam assembly and the rotatable bushing.

As will be apparent to the person skilled in the art in light of theforegoing summary, devices according to the present invention canaccommodate repeated cycling and concomitant wear without having anyresulting increase in backlash clearances manifest as a chuck problem,since the eccentric spring bias on the relative positioning of the rackand pinion will continually position the two to minimize backlashclearance therebetween, not withstanding any normal amounts of wear.Moreover, this bias is such that the normal vibrations of the seat backduring operation of the automobile will in fact result in even morebacklash clearance being taken up. In effect, the present device will,up to a point, manifest less and less chuck during use.

INTRODUCTION TO THE DRAWING

FIG. 1a of the drawings illustrates a preferred embodiment of thepresent invention, as showing an elevated side view of an automotiveseat back recliner hinge, with a proximal side plate removed to revealthe operating components;

FIG. 1b of the drawings is an exploded view of the seat back reclinerhinge of FIG. 1.

FIG. 2 of the drawings depicts an alternate embodiment in accordancewith the present invention, here again as an automotive seat backrecliner hinge with the proximal side plate removed for greater clarity;

FIG. 3a of the drawings is a cross-section through line A--A of FIG. 2as it would appear with both side plates duly positioned;

FIG. 3b is a cross-sectional view through line B--B of FIG. 2, and isshown as the cross-section would appear with both side plates dulypositioned on either side of the hinge;

FIG. 4 depicts the embodiment illustrated in FIG. 1, positioned with theoperable elements arranged in their respective "second" positions; and,

FIG. 5 of the drawings depicts an alternate embodiment wherein the mainpivot is eccentrically mounted on the rotatable bushing.

FIG. 6 of the drawings is a cross-sectional view along line C-13 C ofFIG. 5.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now to FIGS. 1a and 1b of the drawings, there is illustratedan automotive seat back recliner hinge generally designated by thereference numeral 1.

Hinge 1 includes a first hinged member, seat back support arm 2, and asecond hinge member, cushion assembly side plate 3a. These arerespectively secured as is well-known in the art to seat back and seatcushion members of a vehicle seat assembly (not shown). Support arm 2and side plate 3 are mutually relatively rotatable about common pivot 4.A power spring 5 is arranged to assist the return of the automotive seatback towards the upright position, from either a fully or intermediatelyreclined position.

Seat back support arm 2 includes a gear rack 6 which is adapted to beengaged with a pinion spur gear 7. Pinion spur gear 7 is rigidly fixedby any conventional means, such as press-fitting or welding, to shaft 9,as is adjacent ratchet wheel spur gear 8. Thus the two spur gear 7 and 8are mutually dependently rotatable with concentric shaft 9. Shaft 9, inturn, is eccentrically mounted for rotation on a rotatable bushing 10.The eccentric bushing 10 is, as shown, preferably a two part bushingmade up of portions 10a and 10b arranged on mutually opposed sides ofthe two gears 7 and 8. The two parts are preferably mirror images of oneanother, and each have an integral loss defining collar portions 10c.Each of 10a and 10b are operationally connected to each other to rotatein unison about collar portion 10c, by means of, for example, connectingrivet 24 (see FIG. 3a).

Portions 10a and 10b are operationally interconnected to each other torotate in unison with one another in the manner just describedindependently of shaft 9, but about the transitional axis defined by theshaft 9. It will be appreciated that unitary rotation of the bushingportions 10a, 10b within the apertures 21a and 21b in the manner hereindescribed will, due to the eccentric placement of the central apertures10a, 10a, in the collar portions 10c, 10c, cause the axis of shaft 9 tocyclically translate.

The collar portions 10c (on each of 10a and 10b) are respectivelymounted for rotation in apertures 21a and 21b of side plate 3a andproximal side plate 3b. Accordingly, bushing 10 is operable toselectively position the pinion spur gear 7 (which is rigidly attachedto shaft 9) and the rack 6 in a first mutually proximal position, (asshown in FIGS. 1a and 1b), and a second mutually spaced position (asshown in FIG. 4).

A locking pawl 11 is pivotally arranged on side plate 3b, to rotateabout pivot pin 11a and adapted to lockingly engage with and unlockinglydisengage from the ratchet wheel spur gear 8. The locking pawl 11 isoperably positionable in selected first locking, (as illustrated in FIG.1), and second unlocking positions, (as illustrated in FIG. 4)corresponding to the concurrent first mutually proximal and secondmutually spaced positions of pinion gear 7 and gear rack 6.

In operation, the amount of backlash between pinion spur gear 7 and gearrack 6 is reduced when the locking pawl 11, the ratchet wheel spur gear8, the pinion spur gear 7 and the rack 6 are serially engaged inmutually secured relation to prevent relative rotation between thesupport arm 2 and the side plate 3a about their common pivot 4. Thismechanical arrangement also allows backlash to be increased between thepinion spur gear 7 and the gear rack 6, once the locking pawl 11 isserially disengaged from the ratchet wheel spur gear 8. In this latterconfiguration, the relative rotation of support arm 2 and side plate 3aabout their common pivot 4, is facilitated.

As illustrated, the locking pawl 11 and the rotatable bushing 10 areco-operably linked in order to concurrently, and respectively:

engage the ratchet wheel spur gear 8, and eccentrically rotate thepinion spur gear 7 into proximal relation with gear rack 6, with therespective components in their corresponding first positions; and,

disengage the ratchet wheel spur gear 8, and eccentrically rotate thepinion gear 7 into spaced relation from gear rack 6 when the respectivecomponents are in their corresponding second positions.

As already mentioned hereinbefore, FIG. 1 depicts these components intheir respective first positions.

Cam assembly 12 is pivotally arranged on side plates 3a and 3b co-axialpins 12b, 12b with a spring bias that is adapted to normally rotate acam surface 13 into first contacting relation with a cam followersurface 14 of the locking pawl 11. This in turn biases the locking pawl11 into the above-mentioned first locking position as shown in FIG. 1.At the same time, cam assembly 12 is manually operable by way of manuallever 22, to be rotatable contrary to the above-mentioned bias, and intoa second contacting relation with another cam follower surface 30 oflocking pawl 11, which is adapted to move the locking pawl 11 into thesecond unlocking position, as shown in FIG. 4.

Rotatable bushing 10 is itself normally spring biased to position pinionspur gear 7 and gear rack 6 into their first proximal position. Anextension lever arm 24 of cam assembly 12, also pivotally mounted onpivot pin 12b and having a cam surface 16, acts concurrently with theoperation of manual lever 22 on cam assembly 12 (through the agency ofbent tab 26) on a cam follower surface 17 on segment 10a rotatablebushing 10, to rotate bushing 10 and thereby eccentrically positionpinion spur gear 7 and gear rack 6 into their second spaced positions.

As illustrated in FIG. 1, the spring biasing forces on cam assembly 12and rotatable bushing 10, are provided by way of a common spring 18acting in tension between lever arm 20 of the cam assembly 12 andconnecting rivet 24 extending between segments 10a and 10b of bushing10.

Referring now to FIG. 2 of the drawings, there is shown an alternateembodiment to the present invention. Reference numerals on FIG. 2correspond to the same functional elements referenced in FIG. 1. Note,however, that the spring biasing forces on cam assembly 12 and rotatablebushing 10 are provided by way of springs 18a and 18b respectively.Instead of being provided by way of common spring extending in tensionbetween lever arms 20 and 19, the tension is provided between thoserespective lever arms and corresponding points of attachment on aportion 21 of side plate 3a.

Turning now to FIG. 3a of the drawings, there is illustrated across-section taken along line A of FIG. 2. This cross-section gives aclear representation of how the eccentric bushing 10 is mounted betweenside plates 3a and 3b, and supports the pinion spur gear 7 and ratchetwheel spur gear 8 relative to their common shaft 9.

Referring now to FIG. 3b of the drawings, there is illustrated across-section through line B--B of FIG. 2, more clearly illustrateportions of cam subassembly 12. Note in particular that cam extension 15is arranged on a common shaft adjacent primary cam 12a, betweenrespective side plates 3a and 3b.

Referring now to FIGS. 5 and 6 of the drawings, there is illustrated asecond embodiment of the invention wherein a vehicular seat back hinge 1in which the common pivot 4 is rotatably mounted in eccentric bushing 19so as to facilitate backlash adjustment between rack 6 and pinion spurgear 7.

It will be appreciated by those skilled in the art that the eccentricbushing mechanism 19 is substantially similar to that illustrated inFIG. 3a of the drawings and like reference numerals have been used todesignate similar structures in the two embodiments illustrated.Extension 17 of bushing 10 is cooperatively joined to cam assembly 12 byextension 16a. Extension 16a is pivotally connected through the balanceof cam assembly 12 through a pin 20 engaging 1 slot 21 positionedadjacent one end of the extension 16a. Extension 16a is connected toportion 17 of bushing 10 by way of a slot and pin arrangement. Thissupports a certain degree of lost motion between the axial movement ofextension 16a on rotation of the cam assembly 12, prior to rotatingeccentric bushing 10, during the release of the locking pawl 11 fromratchet wheel spur gear 8.

Return spring 18b biases the bushing 10 to the first mutually proximalposition. Upward movement of the free end of manual lever 22 causes thelocking pawl 11 to disengage from locking engagement with the ratchetwheel spur gear 8, and thereby allow rotation of the pinion spur gear 7in a manner generally similar to the mechanism illustrated in FIGS. 1-4.Moreover, extension 16a engages the pin 20 by means of the terminal endof the slot 21 upon such upward travel of the manual lever 22, which inturn causes the eccentric bushin 10 to rotate to the second mutuallyspaced position, so as to increase backlash between the pinion spur gear7 and the rack 6, so as to ease relative rotation of said first 2 andsecond 3 hinge members about the pivot 4.

We claim:
 1. A vehicular seat back-recliner hinge for the selectiveincremental adjustment of the inclination of a backrest relative to aseat cushion, said hinge comprising:first and second hinged members,mutually rotatably arranged about a common pivot, with said first memberhaving a gear rack arranged thereon; a pinion spur gear being fixed toan adjacent ratchet wheel spur gear in mutually dependently rotatablerelation therewith about a common concentric shaft mounted on saidsecond hinged member; said common pivot being eccentrically mounted on arotatable bushing mounted for rotation on said first hinged member, saidbushing being operable during rotation thereof to selectively positionsaid rack and said pinion spur gear in first mutually proximal andsecond mutually spaced positions; a locking pawl arranged on said secondhinged member, and adapted to selectively lockingly engage with, andunlockingly disengage from, said ratchet wheel spur gear, said lockingpawl being operably positionable in selected first locking and secondunlocking positions corresponding to concurrent first mutually proximaland second mutually spaced positions, respectively; means for rotatingsaid bushing in one rotational direction to thereby reduce backlashbetween said pinion spur gear and said rack when said locking pawl, saidratchet wheel spur gear, said pinion spur gear and said rack areserially engaged in mutually secured relation to prevent relativerotation between said hinged members about said pivot and for rotatingsaid bushing in a second opposite rotational direction, to increasebacklash between said pinion spur gear and said rack when said lockingpawl is serially disengaged from said ratchet wheel spur gear to therebyease the relative rotation of said hinged members about said commonpivot.